A 24-year-old woman has haemolytic anaemia. Direct antiglobulin (Coombs) test is negative. Blood film shows fragmented red cells (schistocytes), thrombocytopenia, elevated LDH, low haptoglobin, and haemoglobinuria. Serum creatinine is normal. ADAMTS13 activity is 8% (severely deficient). What is the diagnosis and first-line treatment?
- A HUS — supportive care; avoid plasma exchange (worsens outcomes)
- B Thrombotic thrombocytopenic purpura (TTP) — plasma exchange (PEX) immediately + caplacizumab + corticosteroids ✓
- C Immune-mediated haemolytic anaemia (IMHA) — high-dose steroids and IV immunoglobulin
- D Paroxysmal nocturnal haemoglobinuria (PNH) — eculizumab immediately
Explanation
Severely deficient ADAMTS13 activity (< 10%) with microangiopathic haemolytic anaemia (MAHA — schistocytes, negative Coombs) and thrombocytopenia confirms TTP (immune-mediated or acquired). ADAMTS13 deficiency leads to ultra-large vWF multimers causing platelet microthrombi. Treatment is: plasma exchange (removes inhibitory autoantibodies and replenishes ADAMTS13) + immunosuppression (corticosteroids + rituximab) + caplacizumab (anti-vWF nanobody, reduces thrombotic events and mortality — approved per 2023 guidelines). HUS (caused by STEC) has normal ADAMTS13 and predominantly renal involvement. PNH has haemoglobinuria but not schistocytes and CD59 deficiency on flow cytometry.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.